1. Field of Invention
The present invention is directed to a real-time opto-electronic image processor. In particular, the present invention is directed to a system and method for real-time optical enhancement of imaging object-to-background contrast.
2. Description of Related Art
Presently, it is difficult to track objects, such as endangered wildlife, against varying backgrounds, such as trees or fields. Additionally, aircraft, target and munitions tracking at, for example, flight test center ranges, is becoming increasingly challenging. As the pollution of the surrounding areas of DoD test ranges increases, more pollution is deposited in the air. This pollution causes an increase of airborne particulate, haze, and other phenomenon that reduce visibility. Additionally, aircraft and munitions are moving at higher velocity and some objects are stealthy, making them difficult to track.
A current approach to image enhancement for object tracking involves the use of sensitive infrared cameras and range-gated laser camera systems. Unfortunately, these devices are very expensive. Infrared cameras typically cost tens of thousands of dollars and the cost of range-gated laser camera systems is even more. These approaches are cost prohibitive for intensive use at numerous sites. Another problem with existing systems is that they are active and they xe2x80x9clight-upxe2x80x9d a target or object. That is, they project light or audio signals onto the object for detection. These projections can inform the object that it is being tracked.
FIG. 1(a) illustrates an exemplary observation scenario of a flying target or object 110. The scenario includes the object 110, a sun 120, a cloud 130, a tracker 140, reflected light 150 and scattered light 160. The tracker 140 collects both light scattered 160 in the atmosphere and reflected 150 from an object 110. Therefore, the visibility of the object 110 visibility depends strongly on atmospheric conditions.
The enhancement of object visibility can be achieved by rejecting the signal in those portions of the light spectrum in which the signal from the object 110 is weak but there is a strong signal from the background. Because of strong Rayleigh scattering of blue light, it can be useful to reject the blue portion of the visible spectrum. Although computer algorithms can be used to calculate how these effects influence light propagation in the atmosphere, unfortunately all calculations assume some atmospheric model that can be significantly different from the atmospheric conditions at the point of observation.
The present invention provides a method and a system for a real-time opto-electronic image processor that uses an Acousto-Optic Tunable Filter (AOTF). Image processing can include, for example, object contrast enhancement, object identification, object detection, object tracking or the like. For object contrast enhancement, spectral images at a plurality of spectral intervals are collected. Object and background spectral parameters are established. Filter coefficients are calculated based upon the object and background spectral parameters for maximizing contrast between the object and background in real time. An acousto-optic filter transmission spectrum is adjusted based upon the calculated filter coefficients. An image is captured through the optical filter corresponding to the adjusted acousto-optic filter transmission spectrum.
This system can enhance the visibility of remote objects under test in adverse weather conditions. When installed on an optical target tracker, this system can automatically adjust its spectral transmission in such a way that the intensity of the background illumination will be reduced significantly while providing minimum reduction of the light reflected from a detected object.
An AOTF under computer control is capable of quickly varying the shape of its spectral transmission curve in the entire visible range. The system automatically analyzes the spectral signatures of the background and of the selected object of interest. It calculates a spectrally matched filter for background suppression and object contrast enhancement. This filtered data then goes directly into the optical channel with minimal computer image processing. The resulting image with the enhanced object contrast can be displayed in real time on a common computer monitor and can be recorded by a VCR.
The system makes flight testing of military equipment more informative and less expensive. It reduces flight test program dependence on weather conditions and allows for the collecting of more data by providing real time images with enhanced object visibility.
The system and method of the present invention is capable of automatic real-time accommodation for particular atmospheric conditions in a point of observation. To make this accommodation, initial spectral information about the object and background may be collected. The proposed system can then track an object and provide real time enhanced images until severe variations in object or background spectra occur. Then, new data may be collected and the cycle of observation can be continued.